The present invention relates to an electrochemical reserve battery, and more particularly to such a battery including apparatus for storing and transferring electrolyte from a common reservoir to each cell compartment for activation and immediate operation.
A reserve or deferred action battery consists of two main components: a plurality of cells, anodes, cathodes and separators; and an electrolyte. The electrolyte is physically separated from the cells until electrical energy is needed. Such a battery is useful where it is to be stored for an extended period of time. It has been particularly useful in the newer high energy density lithium batteries which are more prone to explosive reactions after the electrolyte is pumped into the cells.
There are various methods in the prior art for pumping electrolyte into the cells of a reserve battery, but only a few lend themselves to the compact cylindrical configurations required in air-launched buoys and the like. In one embodiment, the electrolyte is initially stored in an expanded bellows and prevented from entering the cells by a burst disk. High pressure gas around the bellows creates a differential pressure. When electrical energy is needed, the burst disk is actuated and ruptured, and the differential pressure collapses the bellows pumping the electrolyte into the cells, thereby activating the battery. Unfortunatey, this embodiment experiences battery failures under certain conditions of vibration. Cracks develop in the bellows when vibrated in the expanded position such that the differential pressure is lost and the electrolyte cannot be pumped into the individual cells. The cracks occur because the bellows, in conjunction with the considerable weight of the electrolyte, acts like a cantilevered beam producing high stresses on the bellows that exceed the design limits.